I'm considering a short (5 days over a weekend) trip to Iceland in early spring (March, maybe April) for a couple in our late 20s. We generally do city trips, but recently took a trip to Australia and had great time touring the red center and want another vacation with lots of natural sites. We would plan on having a rental car. I have a very rough itinerary sketched out below. Generally want to see Reykjavik, Golden Circle attractions, black sand beachs and lava fields, glaciers, northern lights and blue lagoon.

Itinerary:
Day 1 Reykjavík - Arrive in morning and go to hotel. Spend day touring the city and eating lunch and dinner.
Day 2 Golden Circle - Leave in the morning to self-drive to the Golden Circle attractions and spend the night in Selfoss. Look to see Northern Lights during one of the nights on the trip.
Day 3 South Iceland - Leave in the morning and drive to Vik, Skaftafell and Jokulsarlon. Overnight in the area.
Day 4 South Iceland - Drive back to either Selfoss or Reykjavik depending on how far we want to drive, spending more time at the Day 3 sites and covering any sites we weren't able to fit in on Day 3.
Day 5 Reykjavik - Spend the last day touring for a few hours in Reykjavik and then go to Blue Lagoon before evening flight home.

Questions
1. From reading online posts and watching YouTube videos it looks like the weather will be cold, windy and rainy this time of year. We have some experience winter driving, but not too much. Would I be OK driving this time of year, especially since I plan to generally stay on the Ring Road?
2. Given my short time, it looked like South Iceland was the best option but should I consider the Snaefellsnes peninsula instead?
3. Are the places I've listed driveable within the days I've allotted? On day 2, I could drive a bit further than Selfoss. Any recommendations for towns to stay at that would put me at a closer driving distance to Vik and Skaftafell?

Thanks!